JP2021532655A - Resonant cavity surface acoustic wave (SAW) filter - Google Patents

Abstract

The present invention comprises an acoustic wave propagation substrate 102, an input transducer structure 112 and an output transducer structure 114 provided on the substrate, each of which comprises staggered comb tooth electrodes 124, 126. A transducer structure, an output transducer structure, and one reflection structure 116, wherein the reflection structure is a distance from the input transducer structure and the output transducer structure in the propagation direction of the acoustic wave. And, a coupled cavity filter structure using surface acoustic waves, with a reflective structure comprising at least one metal strip 114 located between the input and output transducer structures. The present invention relates to a coupled cavity filter structure, wherein the acoustic wave propagation substrate 102 is a composite substrate including a base substrate 106 and a piezoelectric layer 104. [Selection diagram] FIG. 5a

Description

The present invention relates to surface acoustic wave devices for filter applications, and more particularly to composite substrates for surface acoustic wave filter devices.

In recent years, surface acoustic wave (SAW) devices have been used in more and more practical applications such as filters, sensors, and delay lines.

SAW filter synthesis requires different types of tools and allows different types of structures to be realized. However, the use of conventional filter structures in SAW devices faces various problems, such as device miniaturization and performance.

SAW filter devices typically use wafers made from _{monolithic quartz, LiNbO 3} or LiTaO _{3 crystals as the piezoelectric material.} However, the use of piezoelectric substrates results in high sensitivity to temperature or weak electromechanical coupling, depending on the piezoelectric material used. This results in low performance filter passband characteristics.

Filter performance is defined using several parameters such as bandwidth, intra-band insertion loss, and blocking and transition bandwidth separating the passband and blocking band.

In addition, the use of cavities to generate poles and zeros in the filter transfer function is a well-known technique systematically used when developing microwave filters operating at several GHz. Such filters require a waveguide, with resonant elements located along the waveguide that provide poles or zeros depending on how the resonant elements are connected to each other (in series or in parallel). The synthesis of such filters presupposes a given coupling factor between the signal source and the filter structure, with less ripple in the band and improved out-of-band blocking of these poles and zeros. Based on the combination. In either case, the filters are connected to each other or located along the waveguide and into a series of cavities accessible by electrical connectors or directly through the edges of the waveguide. There is only. Electromagnetic to acoustic wave conversion and vice versa need to be achieved in order to provide the SAW device with an electromagnetically filtered signal. In between, the electrode structures are combined by a technique in which resonances can be combined electrically or acoustically to provide the effect of filtering.

Currently, the solution currently being developed for SAW filters is to combine IDTs using diffraction gratings, both of which operate near Bragg conditions, in order to achieve filter functionality. Based on the impedance element grating (so-called SAW ladder), or a vertically coupled resonator filter (LCRF), or a double mode SAW (DMS) filter, three types of architecture are used. However, these approaches generally allow more than one pole to be placed in the passband, thus resulting in a device with unoptimized performance and require a relatively large occupied area.

An object of the present invention is to provide a surface acoustic wave (SAW) filter device deposited on a composite substrate with an improved design for compactness, simplicity, and versatility, as well as good performance. It is to overcome the above-mentioned drawbacks.

An object of the present invention is an acoustic wave propagation substrate, at least one input transducer structure and one output transducer structure provided on the substrate, each of which is provided with staggered comb tooth electrodes. At least one input transducer structure, one output transducer structure, and one reflection structure, in which the reflection structure is an input transducer structure and an output transducer structure in the propagation direction of the acoustic wave. Surface acoustic waves, particularly guided, comprising one reflective structure comprising at least one metal strip located at a distance d from and between the input and output transducer structures. Achieved by a coupled cavity filter structure using a waved surface acoustic wave, wherein the acoustic wave propagation substrate is a composite substrate comprising a base substrate and a piezoelectric layer. NS. By including such a filter structure, a pass band can be adjusted, and at the same time, a filter structure that occupies a smaller occupied area than the above-mentioned filter structure in the art can be realized.

According to a modification of the present invention, the coupled cavity filter structure may be configured such that the surface acoustic wave is a shear wave or a longitudinal wave in the piezoelectric layer. Whereas Rayleigh waves have been used in the prior art, the use of piezoelectric layers as an alternative to bulk substrates paves the way for the use of different types of acoustic waves, thus providing further optimization parameters. do. Waveguided shear waves can achieve the best electromechanical coupling reachable using composite substrates. They allow for faster wave velocities than elliptically polarized waves, with more opportunities for thermal compensation compared to traditional Rayleigh-like waves. In addition, the use of a given combination of substrate and induction conditions allows to induce longitudinally polarized waved waves, such as shear and Rayleigh waves with greater than 5% coupling. Achieve faster speeds than other wave types.

According to a variant of the invention, the staggered comb tooth electrodes of at least one input transducer structure and one output transducer structure can be defined by the Bragg condition given by p = λ / 2, λ. Is the operating acoustic wavelength of the transducer structure and p is the electrode pitch of the transducer structure. This approach makes it possible to achieve optimal dimensions and induced conditions or coupling states for a given frequency, bandwidth, and energy confinement.

According to a modification of the present invention, the coupled cavity filter structure is an input transducer structure and / or an output transducer on the side opposite to the side where one reflection structure is located in the propagation direction of the acoustic wave. Further, at least one Bragg mirror located away from the structure may be provided. The presence of Bragg mirrors located in close proximity to the transducer structure makes it possible to reduce losses in the structure.

According to a modification of the present invention, the coupled cavity filter structures are separated from each other by a gap g in the propagation direction of the acoustic wave, and at a distance d with respect to the input transducer structure and the output transducer structure. And may include multiple reflective structures located between the input and output transducer structures, each gap g between the reflective structures, and adjacent to the transducer structure and the transducer structure. Each gap d between the reflected structure and the formed reflective structure forms an acoustic cavity. The inclusion of more than one reflective structure in the structure provides the structure with multiple acoustic cavities. More acoustic cavities allow the transition band to be narrowed.

According to a variant of the invention, the dimensions of each acoustic cavity in the cavity filter structure can be less than λ / 4, especially such that the phase velocity in the cavity exceeds the phase velocity in the reflective structure. Such dimensions can improve resonance conditions and thus the performance of the filter.

According to a modification of the present invention, can the distances between adjacent reflective structures of the plurality of reflective structures and / or the distances between the reflective structures and the adjacent transducer structures be the same? Or it can be different. Filter parameters can be improved by adapting the dimensions of the gap and thus the dimensions of the cavity.

According to a modification of the present invention, the one or more reflective structures have a unitary metal strip reflectance coefficient greater than _{the coupling coefficient k s} ² _{of the electrodes of the composite substrate and the transducer structure, in particular the coupling coefficient k s} ^2. It can have a unitary metal strip reflectance coefficient that is at least 1.5 times greater than that. A higher ratio of the reflection coefficient divided by the coupling coefficient is a substantially flat intra-band transfer function, with less in-band ripple effect for a given bandwidth compared to unconditional filters. And a steep transition band.

According to variants of the invention, each reflective structure may comprise at least one metal strip, the pitch of the metal strips being the same as or different from the electrode pitch of the transducer structure. The use of high-reflection structures can give the mirror a higher tolerance for manufacturing variability, while the use of high-reflection structures shifts the zeros of the reflection function to improve out-of-band blocking. It makes it possible to do more.

According to a modification of the present invention, the metal strips of each reflective structure may be electrically connected to each other. Therefore, a constant potential can be achieved across each reflective structure, thus improving the reflectance coefficient of the reflective structure under Bragg conditions.

According to a variant of the invention, the number of metal strips in each reflective structure of the plurality of reflective structures can be less than 30, preferably less than 20, and thus the reflectance coefficients of the plurality of reflective structures. Is greater than 0.5, especially greater than 0.8. Therefore, the cavity confinement of sound energy can be improved and a modal coupling state can be provided in the structure.

According to a modification of the present invention, the difference between the acoustic impedance of the material from the piezoelectric layer and the material from the metal strip of each reflective structure of the plurality of reflective structures is the reflectance coefficient of the plurality of reflective structures. It can be greater than 0.5, especially greater than 0.8. By increasing the reflection coefficient, it is possible to reduce the dimensions of the filter structure.

An object of the present invention is an acoustic wave propagation substrate, at least one input transducer structure and one output transducer structure provided on the substrate, each of which comprises an electrode. A structure, one output transducer structure, and one reflection structure, wherein the reflection structure is at a distance L from the input transducer structure and the output transducer structure in the propagation direction of the acoustic wave. A coupled cavity filter using surface acoustic waves, particularly waveguideed surface acoustic waves, with one reflective structure, including a groove located between the input transducer structure and the output transducer structure. Further achieved in the structure is a coupled cavity filter structure characterized in that the acoustic wave propagation substrate is a composite substrate comprising a base substrate and a piezoelectric layer. By including such a filter structure, a pass band can be adjusted, and at the same time, a filter structure that occupies a smaller occupied area than the above-mentioned filter structure can be realized in the art.

According to a modification of the present invention, the coupled cavity filter structure may be configured such that the surface acoustic wave is a shear wave or a longitudinal wave in the piezoelectric layer. Whereas Rayleigh waves have been used in the prior art, the use of piezoelectric layers as an alternative to bulk substrates paves the way for the use of different types of acoustic waves, thus providing further optimization parameters. Waveguided shear waves can achieve the best electromechanical coupling reachable using composite substrates. They allow for faster wave velocities than elliptically polarized waves, with more opportunities for thermal compensation compared to traditional Rayleigh-like waves. In addition, the use of a given combination of substrate and induction conditions allows to induce longitudinally polarized waved waves, such as shear and Rayleigh waves with greater than 5% coupling. Achieve faster speeds than other wave types.

According to a modification of the present invention, the coupled cavity filter structure is an input transducer structure and / or an output transducer on the side opposite to the side where one reflection structure is located in the propagation direction of the acoustic wave. It may further include at least one additional groove located away from the structure. The presence of grooves located in close proximity to the transducer structure can be configured to reduce losses in the structure and, for example, to provide total internal reflection of acoustic waves propagating in the transducer.

According to variations, the electrodes of at least one input transducer structure and one output transducer structure can be defined by an electrode pitch p equal to nλ, where λ is the operating acoustic wavelength of the transducer structure.

According to a variant, the coupled cavity filter structure is from the input transducer structure and / or the output transducer structure on the opposite side of the acoustic wave propagation direction to the side where one reflection structure is located. Further, at least one additional groove located at a distance may be provided.

According to a variant, at least one additional device located away from the input and / or output transducer structure on the opposite side of the acoustic wave propagation direction to which one reflection structure is located. The groove depth D ₃ can be on the order of λ or more (about λ or more).

According to a modification, the coupled cavity filters are separated from each other by a gap g and in the propagation direction of the acoustic wave, at a distance L from the input transducer structure and the output transducer structure, and the input transducer structure. A plurality of reflective structures located between the and the output transducer structure may be provided, and each gap g between the reflective structures forms an acoustic cavity. According to the modification, between the edge of the groove and the positions A and B corresponding to the end of the pitch of the transducer structure (812, 814) on the side where the groove is located in the propagation direction of the acoustic wave. Distance L ₂ can form an acoustic cavity. The inclusion of more than one reflective structure in the structure provides the structure with multiple acoustic cavities. More acoustic cavities allow the transition band to be narrowed.

According to the variant, the distance between the edge of the groove (822, 1022, 1322, 1422, 1522, 1722) and the edge of at least one additional groove (932, 934) is on the order of nλ. obtain. Such dimensions can improve resonance conditions and thus the performance of the filter.

According to the variant, when the clearance angle is the angle between the horizontal axis X and the edge wall of the groove, the clearance angle of the groove of the reflective structure can be on the order of 70 ° or more, especially on the order of 90 °. ..

According to the modification, the depth of the groove of the reflection structure is on the order of λ or more, particularly on the order of 10λ or more, where λ is the wavelength of the surface acoustic wave.

According to the variant, at least one additional groove is configured to, for example, provide total internal reflection of the propagating wave along the propagating direction.

According to the variant, the acoustic cavity formed between at least two grooves of the plurality of reflective structures can be located on the surface of the substrate, which is also the surface of the substrate on which the transducer is located.

According to the modification, the acoustic cavity formed between at least two grooves of the plurality of reflective structures has a depth included between the surface of the substrate and the bottom surface of at least two grooves located at depth D. Can be located.

According to the variants, the input transducer structure and the output transducer structure can be different, and in particular, the number of electrode fingers in each transducer structure can be different. Therefore, the filter structure is more versatile and the transducer structure can be modified to optimize mode coupling efficiency within the reflective structure in order to achieve low insertion loss.

According to a modification of the present invention, acoustic cavities can be divided into subcavities that are separated from each other. The subcavities can be separated from each other by additional layers, allowing an evanescent bond to be created from one cavity to another. Therefore, the subcavities can favor energy confinement in the structure and result in improved miniaturization of the device.

According to a modification of the present invention, the cavity filter structure comprises at least three transducer structures in the direction of sound wave propagation. The signal source density can be increased to achieve improved containment. Moreover, the filter band can be flatter than that for the same filter containing only two transducers.

According to variants of the invention, in particular, the shape of the transducer structure, eg, the thickness, width, and / or length of the electrode, and / or number, and / or not only the shape, but also the wavelength. Sheep waves, preferably waveguideed or waveguideed waves in the piezoelectric layer, to achieve higher filter band-passing characteristics by adapting the thickness of the piezoelectric layer, which must be greater than or equal to 5% of λ. It was as electromechanical coupling factor k _s ² of the longitudinal wave is greater than 5%, as in particular greater than 7%, the characteristics of the piezoelectric layer, and characteristics of the electrodes of the transducer structure may be selected.

According to a variant of the invention, shear wave in the piezoelectric layer (104), shear wave guided, or electromechanical coupling factor k _s ² of waveguided longitudinal wave is greater than 5% is preferably As such, the thickness of the piezoelectric layer can be selected, in particular to be greater than 7%. For larger and larger thicknesses than λ, the acoustic wave loses its waveguide properties, resulting in the emission of multiple waves in the layer and energy loss in the substrate.

According to a modification of the present invention, the cavity filter structure may further include a dielectric layer sandwiched between the base substrate and the piezoelectric layer, particularly a SiO ₂ layer. The dielectric or passivation layer can improve the mounting of the piezoelectric layer on the base substrate, but can further improve electromechanical coupling while maintaining the temperature stability of the surface acoustic wave device. The dielectric layer preferably has a thickness of less than 1 μm, particularly in the range of 100 nm to 1 μm.

According to a modification of the present invention, the piezoelectric layer of the composite substrate includes aluminum nitride (AlN), zinc oxide (ZnO), PZT, potassium niobate KNbO ₃ , and similar materials such as KTN, and a piezoelectric relaxer. For example, PMN-PT and related materials, gallium nitride (GaN), lithium tantalate LiTaO ₃ , or lithium niobate LiNbO ₃ , where the lithium tantalate LiTaO ₃ or lithium niobate LiNbO ₃ can be used. _{With a crystal orientation relative to lithium tantalate LiTaO 3} or lithium niobate LiNbO ₃ , defined as (YXl) / θ according to the standard IEEE1949Std-176, the crystal orientation angle θ is between 0 ° and 60 °, or 90. Included between ° and 150 °.

According to a modification of the present invention, the base substrate of the composite substrate can be one of silicon, particularly a high resistivity silicon substrate including a trap-rich layer, carbon diamond, sapphire, or silicon carbide. With high resistivity, it is possible to understand electrical resistivity higher than 1000 ohm cm. In order to transfer the piezoelectric layer to silicon, the layer is transferred by ion implantation into a pressure power supply substrate to define the layer to be transferred, mounting the source substrate on the silicon substrate, and thermal or mechanical treatment. Mass production methods such as SmartCut ™ can be used. A simpler approach based on joining the piezoelectric substrate to the base substrate and subsequent thinning of the piezoelectric substrate (via CMP, grinding, polishing) may be used for the present invention, in particular, in particular. Suitable for thick piezoelectric layers that are expected to have a final thickness on the order of 5 μm to 20 μm. Both approaches of layer transfer via Smart Cut ™ or layer transfer via ligation / thinning result in high quality single crystal piezoelectric layers formed on the base substrate.

According to a modification of the present invention, the base substrate may include a Bragg mirror below the piezoelectric layer. Bragg mirrors consist of a stack of periodically alternating layers of acoustic impedance deposited or manufactured on a plate of any inorganic material. The stack of layers behaves like a mirror to the waves induced in the upper piezoelectric layer, provided that the thickness of each layer is approximately one-fourth of the acoustic wavelength. Therefore, the mirror reflects a wave having a component pointing in the depth direction of the substrate and traps the wave in the piezoelectric layer.

According to a modification of the present invention, the coupled cavity surface acoustic wave filter structure results in filter band passage included between 0.5% and 10%. By changing the parameters of the cavity filter structure, it is possible to change the bandpass of the filter device, and therefore the device can be adapted to the user's specifications to achieve the required filter bandpass.

According to a modification of the invention, the coupled cavity filter structure may further comprise a passion layer formed on a transducer structure and at least one reflective structure, wherein the passivation layer is the transducer structure and / Or have the same or different predetermined thickness on at least one reflective structure.

The object of the present invention is further achieved by using a SAW ladder filter device with at least two coupled cavity filters described above, the at least two coupled cavity filter devices may be located on a single line. Since the coupled cavity filter according to the present invention can be located on a single line, the arrangement and connection of a plurality of cavity filters does not require as much space as a conventional SAW ladder device. The SAW ladder filter device according to the present invention is a smaller device than the conventional SAW ladder filter device.

The invention can be understood by reference to the following description which is considered in conjunction with the accompanying drawings, in which the reference numerals identify the features of the invention.

It is a figure which shows the coupling type cavity surface acoustic wave filter structure by 1st Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 1st Embodiment of this invention. It is a figure which shows the coupling type cavity surface acoustic wave filter structure by 2nd Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 2nd Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 2nd Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 2nd Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 2nd Embodiment of this invention. Coupled cavity surface acoustic waves, including a composite substrate according to the invention, comprising a _{500 nm SiO 2} layer between a 6 μm LiTaO ₃ (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate. It is a figure which shows the performance of a filter structure. Coupled cavity surface acoustic waves, including a composite substrate according to the invention, comprising a _{500 nm SiO 2} layer between a 6 μm LiTaO ₃ (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate. It is a figure which shows the performance of a filter structure. Coupled cavity surface acoustic waves, including a composite substrate according to the invention, comprising a _{500 nm SiO 2} layer between a 6 μm LiTaO ₃ (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate. It is a figure which shows the performance of a filter structure. Coupled cavity surface acoustic waves, including a composite substrate according to the invention, comprising a _{500 nm SiO 2} layer between a 6 μm LiTaO ₃ (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate. It is a figure which shows the performance of a filter structure. It is a figure which shows the table which listed the characteristic of the coupled cavity surface acoustic wave filter structure shown in FIG. 2b by this invention. It is a figure which shows the coupling type cavity surface acoustic wave filter structure by the 3rd Embodiment of this invention. It is a figure which shows the coupling type cavity surface acoustic wave filter structure by the 3rd Embodiment of this invention. It is a figure which shows the coupling type cavity surface acoustic wave filter structure by 4th Embodiment of this invention. It is a figure which shows the coupling type cavity surface acoustic wave filter structure by 5th Embodiment of this invention. It is a figure which shows the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the modification of the coupling type cavity surface acoustic wave filter structure by 6th Embodiment of this invention. It is a figure which shows the device by the 3rd Embodiment of this invention used for a practical example of a simulation. It is a figure which shows the characteristic by the simulation of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 by the 3rd Embodiment of this invention. It is a figure which shows the characteristic by the simulation of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 by the 3rd Embodiment of this invention. FIG. 5 is a diagram showing the effect of device parameters on the simulated characteristics of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 according to the third embodiment of the present invention. FIG. 5 is a diagram showing the effect of device parameters on the simulated characteristics of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 according to the third embodiment of the present invention. FIG. 5 is a diagram showing the effect of device parameters on the simulated characteristics of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 according to the third embodiment of the present invention. FIG. 5 is a diagram showing the effect of device parameters on the simulated characteristics of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 according to the third embodiment of the present invention. It is a figure which shows the example of the SAW ladder filter device by the prior art in FIG. 12a. It is a figure which shows the example of the SAW ladder filter device by this invention in FIG. 12b.

FIG. 1 shows a coupled cavity surface acoustic wave filter structure according to the first embodiment of the present invention. In FIG. 1a, the coupled cavity surface acoustic wave filter structure 100 is realized in the substrate 102 which is a composite substrate. The composite substrate 102 includes a layer of piezoelectric material 104 having crystal axes X, Y, and Z formed on the base substrate 106.

The piezoelectric layer 104 in this embodiment is defined by (YXl) / θ in accordance with the standard IEEE1949Std-176, in particular, the crystal orientation angle θ is included between 0 ° and 60 °, or between 90 ° and 150 °. _{LiTaO 3} or LiNbO ₃ , potassium niobate KNbO ₃ , and similar material compositions with similar cut orientations, such as KTN, and other piezoelectric layers using a sputtering or epitaxial film, such as aluminum nitride AlN. , Zinc oxide ZnO, PZT, GaN or any composition of AlN and GaN.

The thickness of the piezoelectric layer 104 formed on the base substrate 106 is on the order of one wavelength λ or less, particularly about 20 μm or less. The thickness t of the base substrate 106 is larger than the thickness of the piezoelectric layer 104. A preferred situation corresponds to a base substrate thickness that is at least 10 times greater than the thickness of the piezoelectric layer 104, particularly 50 to 100 times larger, which corresponds to a base substrate thickness equal to 250 μm to 500 μm.

The base substrate 106 used in the first embodiment of the present invention is a silicon substrate, particularly a high resistivity silicon substrate. The orientation of the silicon substrate is preferably (100) because of the higher acoustic wave propagation speed than other crystal orientations such as (110), (111) or (001), for example, but (110), ( Other crystal orientations such as 111) or (001) may also be used. Instead of silicon, other substrate materials with acoustic wave propagation velocities greater than one of the piezoelectric layers may be selected, for example carbon diamond, sapphire, or silicon carbide may be used.

In a modification of the present invention, the base substrate 106 may further include a so-called trap-rich layer close to the upper layer of the piezoelectric material, which improves the insulating performance of the base substrate and is polycrystalline, amorphous, or porous. It may be formed of a quality member, for example, at least one of polycrystalline silicon, amorphous silicon, or porous silicon, but the invention is not limited to such materials.

In a modification of the present invention, the base substrate 106 may further include a Bragg mirror below the piezoelectric layer 104. Bragg mirrors consist of a stack of periodically alternating layers of acoustic impedance deposited or manufactured on a plate of any inorganic material. Acoustic impedance is the product obtained by multiplying the material density in the wave speed is represented by Rayleigh, M Rayleigh, i.e. it is preferably represented by the 10 ⁶ Rayleigh. Piezoelectric layers are deposited or manufactured on a layer stack for the induction and detection of acoustic waves. It is useful that the stack consists of tungsten and silica, or _{an alternation of Si 3} N ₄ and SiO ₂ , or Mo and Al, and generally any combination of materials with an acoustic impedance ratio greater than 2. Can be done. It can be beneficial for the inorganic subplate to be standard silicon, or high resistivity silicon or glass, and generally any material with a coefficient of thermal expansion (TCE) of less than 6 ppm / K. Further trap-rich layers may be incorporated to improve electrical insulation. It is useful that the first layer of the stack can be SiO ₂ , or in general any material that can be used to bond the piezoelectric layer to the composite substrate described above.

In this embodiment, a thin SiO ₂ layer 108 is provided at the interface 110 between the piezoelectric layer 104 and the base substrate 106 in order to improve the attachment of the piezoelectric material layer 104 to the base substrate 106. The SiO ₂ layer 110 has a thickness of 200 nm, but in the modified example, _{the thickness of the SiO 2} layer 110 may vary. It can be larger or smaller than a thickness of 200 nm, and in particular can vary between 10 nm and 6 μm.

The coupled cavity filter structure 100 consists of two transducer structures 112, 114 and two transducer structures 112 at a specific distance d from the transducer structures 112, 114 in the propagation direction X shown in FIG. , And one reflective structure 116 located between 114. A region located between the reflective structure 116 and one transducer structure 112, 114, eg, a region 118 having a width thereof defined by a distance d, corresponds to the acoustic cavity 120. In this case, the electrode has a center within the pitch p of the transducers 112, 114. Therefore, in the following, the end of the pitch p of the transducer structures 112, 114 is located at a distance from the electrode 128. In one example, if the ratio a / p of the transducer structures 112, 114 is 50%, the end of the pitch p is only a distance equal to λ / 8 from the first electrode 128 of the transducer structures 112, 114. is seperated.

As a result, the acoustic cavity extends between the reflective structure 116 and the end of the pitch p of the transducer structures 112, 114 on the side where the reflective structure 116 is located. Therefore, in the coupled cavity surface acoustic wave filter structure 100, various acoustic cavities exist in the propagation direction of the acoustic wave, and in the coupled cavity filter structure shown in FIG. 1a, there are two acoustic cavities 120.

The reflective structure 116 typically comprises one or more metal strips 122 and is defined by the pitch of the metal strips 122 (not shown) corresponding to the distance between the metal strips 122 within the reflective structure 116. .. As with the transducer structures 112, 114, the pitch in the reflective structure 116 is defined by including a metal strip having a center within the pitch.

The transducer structures 112 and 114 correspond to the input transducer structure 112 and the output transducer structure 114, but in the direction of acoustic wave propagation, the input transducer structure is on the right side of the structure and is output. The positions of the input transducer structure 112 and the output transducer structure 114 may be exchanged so that the transducer structure is on the left side of the structure. The E code represents the input acoustic signal of the transducer structure, while the S code represents the output acoustic signal of the transducer structure.

Each transducer structure 112, 114 comprises two staggered comb tooth electrodes 124, 126, each comprising a plurality of electrode means 128, 130, respectively. In this embodiment, the electrode means 128 and 130 have the shape of an electrode finger. The electrode fingers 128, 130 of the comb tooth electrodes 124, 126, and the comb tooth electrodes 124, 126, respectively, are Al-doped with an aluminum-based material such as pure aluminum or an aluminum alloy such as Cu, Si, or Ti. Is formed from. Nevertheless, due to the smaller electrode relative thickness, other materials may be used that result in a stronger reflectance coefficient. In that respect, preferred electrode materials are copper (Cu), molybdenum (Mo), nickel (Ni), eg platinum (Pt) or platinum (Pt) containing an adhesive layer such as titanium (Ti) or tantalum (Ta) or chromium (Cr). Gold (Au), zirconium (Zr), palladium (Pd), iridium (Ir), tungsten (W) and the like.

Transducer structures 112, 114 correspond to an inter-edge electrode finger distance between two adjacent electrode fingers 128, 130 from opposite comb tooth electrodes 124, 126, electrode pitch p (not shown). Further stipulated by. In a modification of the present invention, the electrode pitch p is defined by the Bragg condition given by p = λ / 2, where λ is the operating acoustic wavelength of the transducer structures 112, 114. Due to the operating acoustic wavelength λ, λ is the acoustic wavelength based on λ = V / f, where f is the predetermined center frequency of the filter structure and V is the phase velocity of the mode in which it is used. Can be understood. Such transducer structures are also referred to as alternating transducers (IDTs) with two fingers per wavelength.

In a variant of the invention, the staggered transducer may be, for example, a 3-finger or 4-finger induced structure per wavelength, a 5-finger transducer per 2 wavelengths, or 7 or 8 fingers per 3 wavelengths. Can be used to operate outside of Bragg conditions.

The transducer structures 112 and 114 can be symmetrical, i.e., the transducer structures 112 and 114 include the same number of electrode fingers 128, 130 with the same properties. However, in the modifications of the present invention, the transducer structures 112 and 114 may be different, in particular the transducer structures 112 and 114 may include a different number of electrode fingers 128, 130.

The electrode fingers 132, 134 of the comb tooth electrodes 128, 130 all have substantially the same length l, width w, and thickness h. According to a modification of the embodiment, the electrode fingers 132, 134 may have different length l, width w, and thickness h. Dimensions, so as to achieve the desired coupling coefficient k _s, or other features, for example, removal of the transverse mode, modulation of the IDT impedance configured to utilize a like reduction in the undesired modes emitted.

In a modification of the present invention, the transducer structures 112, 114 may be charred, which means that the electrode pitch p in the transducer structure is continuously changed linearly or hyperbolic. Means that you can. This makes it possible to widen the operating frequency band of the transducer and can provide some robustness to temperature.

The pitch of the metal strip 122 of the reflective structure 116 can be the same as the electrode pitch p of the transducer structures 112, 114. In the modification, the pitch of the metal strip 122 of the reflective structure 116 may be different from the electrode pitch p of the transducer structures 112, 114.

In a modification of the invention, the reflective structure 116 is similarly chapped to increase the operating band of the filter and to increase the resonance efficiency of the acoustic cavity 118 located between the transducer structures 112, 114. Can be done.

In a modification, the coupled cavity filter structure 100 further comprises two Bragg mirrors 132, 134. An example of this modification is shown in FIG. 1b, where the Bragg mirrors 132, 134 are located on the outside of the coupled cavity filter structure 200, in close proximity to the transducer structures 112, 114, which is not the case. It means that the reflection structure 116 is located on the opposite side of the propagation direction of the acoustic wave. Each Bragg mirror 132, 134 is located at a distance s from the transducer structures 112, 114 of the Bragg mirrors 132, 134, respectively. Each Bragg mirror 132, 134 comprises one or more metal strips 136 and is defined by the pitch (not shown) of the metal strips 136 corresponding to the distance between the metal strips 136 within the Bragg mirrors 132, 134. There is.

In a modification of the present invention, the reflective structures 116 and the Bragg mirrors 132, 134 may be constructed by etching grooves instead of depositing metal strips 136, 210. The grooves may be etched downward in the piezoelectric layer 104 of the composite substrate 102 and further down to the base substrate 106.

In a modification, a passivation layer (not shown) may be formed on the transducer structures 112, 114 and at least one reflective structure 116. The passivation layer has the same or different predetermined thickness on the transducer structures 112, 114 and / or at least one reflective structure 116. The passivation layer may be formed on the Bragg mirrors 132, 134. In this modification, the substrate may be a monolithic piezoelectric wafer, such as a lithium tantalate bulk wafer or a lithium niobate bulk wafer, and the passivation layer may be a silica SiO ₂ layer or a tantalum pentoxide Ta ₂ O ₅ layer. Can be beneficial. In this embodiment, the passivation layer has a positive coefficient of thermal expansion (TCE), whereas the substrate has a negative coefficient of thermal expansion (TCE), and the layer thickness is the temperature coefficient of the frequency of the SAW device (TCF). Set to be smaller.

2a to 2e show a coupled cavity filter structure according to a second embodiment of the present invention and a modification thereof. For all of FIGS. 2a-2e, the coupled cavity filter structure is shown in 2D plan view and the substrate on which the coupled cavity filter structure is located is no longer shown. However, the substrate is the same as the substrate 102 of FIGS. 1a and 1b. The same reference numerals as those shown in FIGS. 1a and 1b are used to represent the same features and are not repeated in detail.

In FIG. 2a, the coupled cavity filter structure 300, like the coupled cavity filter structure 200, includes two Bragg mirrors 132, 134, each located in close proximity to one transducer structure. It comprises two transducer structures 112, 114. The difference from the coupled cavity filter 200 is that a plurality of reflective structures, i.e., four reflective structures 202, 204, 206, 208 are present between the transducer structures 112, 114. Each reflective structure 202, 204, 206, 208 of the plurality of reflective structures comprises at least one metal strip 210 at a distance between the metal strips 210 within each reflective structure 202, 204, 206, 208. It is defined by the pitch of the corresponding metal strip 210 (not shown). In this example, each reflective structure 204, 206, 208, 210 has a total of four metal strips 210, but the number of metal strips may be more or less. Of the plurality of reflective structures, the reflective structures 204, 206, 208, 210 may include the same number of metal strips 210, but in the modified example, each of the reflective structures may contain a different number of metal strips 210. good. For example, the number of metal strips 210 in reflective structures 204, 206, 208, 210 may be between reflective structures 204, 206, between transducer structures 112, 114, to enhance resonance at the actual center of the structure. It may increase and then decrease over the entire 208 and 210.

These reflective structures 202, 204, 206, 208 are separated from each other by a gap g. Regions located between two adjacent reflective structures, eg, 202 and 204 having the width defined by the gap g, correspond to the acoustic cavity 212. As with the coupled cavity filter structures 100 and 200, the region located between the reflective structure and the adjacent transducer structure further corresponds to the acoustic cavity 214, but adjacent to the reflective structure. It has a width defined by the distance d from the transducer structure. As in the case of the first embodiment, the electrodes of the transducer structures 112 and 114 have a center within the pitch p of the transducers 112 and 114, and the acoustic cavity has the reflection structure 116 and the reflection structure 116. It is defined as a region located between the end of the pitch p of the transducer structures 112, 114 on the positioned side.

Thus, in a coupled cavity surface acoustic wave filter structure, various cavities are separated by a reflective structure and exist in the direction of acoustic wave propagation, or otherwise, there are two cavities between the transducers. Surrounded by reflective structures. Therefore, in the coupled cavity filter structure 300 shown in FIG. 2a, a total of five acoustic cavities 212 and 214 are present in the mode propagation direction. For a given number of reflective structures between the transducer structures, and with the transducer structures operating under Bragg conditions, the number of acoustic cavities is equal to the number of reflective structures plus one.

In a modification of the present invention, the reflective structures 202, 204, 206, 208 are used to widen the operating band of the filter and the resonance efficiency of the acoustic cavities 212, 214 located between the transducer structures 212, 214. Can be charmed as well to enhance.

In a modification of the invention, the reflective structures 202, 204, 206, 208 and the Bragg mirrors 132, 134 may be constructed by etching grooves instead of depositing metal strips 136, 210. The grooves may be etched downward in the piezoelectric layer 104 of the composite substrate 102 and further down to the base substrate 106.

In a modification of the invention, the metal strips 136, 210 of the reflective structures 202, 204, 206, 208 and / or the Bragg mirrors 132, 134 may be electrically connected to each other. An example of a modification in which both the reflective strips 136, 210 of the reflective structures 202, 204, 206, 208 and the Bragg mirrors 132, 134 are connected to each other is shown in FIG. 2b with respect to the coupled cavity filter structure 400. This results in an improvement in the reflectance coefficients of the reflective structures 202, 204, 206, 208, and Bragg mirrors 132, 134 under Bragg conditions. All of the reflective structures 202, 204, 206, 208 and / or Bragg mirrors 132, 134 operate in so-called short circuit conditions, which means that given reflective structures 202, 204, 206, 208 / Bragg mirror 132. , 134 metal strips 136, 210 are all connected to each other, meaning that they provide a constant potential over the grating structure.

In a variant of the invention, the coupled cavity filter structure may include three or even more transducer structures. FIG. 2c shows a modification in which the three transducer structures 402, 404, 406 are present in the coupled cavity filter structure 400. Further, since the plurality of reflective structures include a total of six reflective structures 302, 304, 306, 308, 310, 312, the coupled cavity filter structure 400 is the coupled cavity filter structure shown in FIG. 2a. Different from 300. Similarly, the same reference numerals are used to account for the coupled cavity filter structure 300 with the same features already described in FIG. 2a.

The two transducer structures 112, 114 are located outside the reflective structures 302, 304, 306, 308, 310, 312, as in the structure of FIG. 2a, and the third transducer. The structure 314 is located in the center of the reflective structures 302, 304, 306, 308, 310, 312116 and therefore, on each side of the third transducer structure 314, the three reflective structures 302, 304, There are 306 and 308, 310, 312. Further, the transducer structure 314 is a reflective structure in which the transducer structures 112 and 114 and the transducer structures 112 and 114 are close to each other (in this example, 302 with respect to the transducer structure 112 and a transducer structure). It is separated from the two adjacent reflective structures by a distance d corresponding to the same distance as the distance to 312) with respect to the object 114. Therefore, the coupled cavity filter 500 includes a total of eight acoustic cavities 316. Such a cavity filter structure 500 is symmetric and results in stronger confinement of energy in the cavity 316 compared to the cavity filter structure 300 shown in FIG. 2a, which contains only two transducer structures 112, 114.

In a modification of the invention, the coupled cavity filter structure is not symmetrical because the third transducer 314 is not located in the center of the coupled cavity filter structure.

In a modification of the present invention, the plurality of acoustic cavities can be divided into subcavities. An example of this modification is shown in FIG. 2d, in which the subcavities are separated from each other by the presence of additional layers. Similarly, the coupled cavity filter structure 600 is different from the coupled cavity filter structure 300 shown in FIG. 2a, as the plurality of reflective structures further comprises a total of three reflective structures 402, 404, 406. .. Similarly, the same reference numerals are used to account for the coupled cavity filter structure 300 with the same features already described in FIG. 2a. In the cavity filter structure 600, the reflective structures located between the reflective structures 402, 404, 406, and the transducer structures 112, 114 and the adjacent reflective structures 402, 406 of the transducer structures 112, 114, respectively. The acoustic cavity 408 located in between is divided into two sections, resulting in the presence of eight dark regions 410 and four white regions 412 between the two transducer structures 112, 114. The dark region 410 represents a position where the wave velocity is lower than the wave velocity in the white region 412, thus providing better energy confinement than the energy confinement in the coupled cavity filter structure 300 shown in FIG. 2a. Therefore, the coupled cavity filter structure 600 provides additional poles, leading to an improvement in the miniaturization of the coupled cavity filter structure 600.

In a modification of the present invention, the input transducer structure and the output transducer structure are neither symmetrical nor identical, and this modification is shown in FIG. 2e. Similarly, the coupled cavity filter structure 700 is different from the coupled cavity filter structure 300 shown in FIG. 2a, as the plurality of reflective structures further comprises two reflective structures 502, 504 in total. Similarly, the same reference numerals are used to account for the coupled cavity filter structure 300 with the same features already described in FIG. 2a. In FIG. 2, the number of electrode fingers of each transducer structure is different. In the coupled cavity filter structure 700, the transducer structure 114 has staggered comb tooth electrodes 124 including five electrode fingers 128, 130, respectively, having a constant electrode pitch p throughout the transducer structure 114. , 126. The transducer structure 506 comprises staggered comb-tooth electrodes 508, 510, each of which includes eight electrode fingers 128, 130, and a third electrode of the comb-tooth electrode 508. There is a gap in the transducer structure 506 between the finger 128 and the fourth electrode finger 130 of the comb electrode 510. Further, in this variant, there is no Bragg mirror in close proximity to the transducer structures 114, 506, which results in greater loss and ripple than the coupled cavity filter structure 300 of FIG. 2a. However, this coupled cavity filter structure 700 is smaller than the structure shown in FIG. 2a and realizes a simpler design.

The coupled cavity surface acoustic wave filter structure functions by the following technique. The input staggered transducers (IDTs) emit sound energy towards the reflective structure to induce resonance in the reflective structure. A reflective structure is bound to another reflective structure, thus creating a coupled state that results in energy transfer from one reflective structure to another. Although multiple such reflective structures can be coupled together, there is at least one output transducer structure that collects the transmitted energy.

Therefore, the present invention utilizes a waveguide of an upper piezoelectric layer from a composite substrate and a coupled cavity filter structure using an acoustic resonant cavity that couples energy from one reflective structure to another. Suggest to use things.

In the case of a coupled cavity filter structure, resonance of the transducer structure occurs in the low frequency transition band of the filter and antiresonance occurs approximately in the center of the filter band. Therefore, a given mode must have a coupling factor proportional to the bandpass achieved, so the conditions for the electromechanical coupling coefficient are similar to those required for an impedance filter, i.e. The coefficient must be 1.5 to 2 times larger than the band achieved, making it possible to reduce insertion loss within this band. However, a reflection coefficient larger than the coupling coefficient, ideally 1.5 times or more the coupling coefficient, is required to realize the filter band.

According to the present invention, even when the coupling coefficient of the transducer structure is 5% or more, the relationship of the reflection coefficient with respect to the coupling coefficient can be realized by using the composite substrate. This is especially true when using waveguide shear waves or longitudinal waves in the piezoelectric layer of the composite substrate.

Due to the thickness of the piezoelectric layer smaller than the wavelength, shear wave mode or longitudinal mode is guided in the piezoelectric layer. Further, the energy loss in the composite substrate can be reduced. The thickness of the piezoelectric layer must be at least 5% of the wavelength λ. For thick piezoelectric layers, the shear mode of the composite substrate is no longer completely guided, but contains a lossy bulk component that reflects off the base substrate at the interface, resulting in a parasitic mode or rattle effect. However, for thin piezoelectric layers, i.e. wavelengths or sub-wavelength thicknesses, the shear mode is completely guided without lossy bulk mode.

The figure of merit of the filter device is the transmittance of the filter indicating the filter band passage as a function of frequency, and the level of loss in the band pass is expressed in dB. Filter band passage depends on various factors: coupling factor, number of cavities, and reflection coefficient.

Very low according to the design and selection of the transducer structure, depending on the dimensions of the piezoelectric layer, the dimensions of the transducer structure, the length of the reflective structure, the number of coupled reflective structures, and the coupling coefficient of the mode. That is, it is possible to synthesize multi-pole and zero-point filters with insertion losses better than 2 dB, especially less than 1 dB, with 15 dB to 20 dB or even greater inhibition.

With respect to the dimensions of the acoustic cavity, the acoustic cavity is ideally a quarter wavelength length or an odd number of quarter wavelengths in order to satisfy the optimum resonance condition, according to the prior art. I have to hang out. In the present invention, the length of the acoustic cavity can be shorter than a quarter wavelength. This is due to the strong velocity change from the free surface to the grating area, resulting in a much larger acoustic impedance mismatch than is reachable using standard true SAW solutions.

With respect to the coupling coefficient, and for the composite substrate and for the metal strip parameters (material, dimensions), the coupling coefficient is directly related to the bandpass value by the coefficient 0.7 and is therefore required of the filter device. Bandpassing can be achieved by selecting the material and dimensions of the cavity filter structure.

With respect to the number of metal strips in the reflective structure, the number is broader than 0.5, especially greater than 0.8, to allow confinement of sound energy in the cavity and thus to result in a modal coupling state. Selected to provide a reflectance factor.

As already mentioned, the magnitude of the reflection coefficient is preferably larger than the coupling coefficient and ideally 1.5 times or more higher than the coupling coefficient parameter. The higher the reflectance coefficient, the smaller the number of metal strips and therefore the wider the filter bandwidth. For example, a reflectance of greater than 15% makes it possible to reduce the number of metal strips that make up the reflective structure, which directly affects the bandwidth of the filter, i.e. the reflectance of the structure. The smaller the number of metal strips in the reflective structure, the wider the bandwidth, provided that is 50% or more. Given a reflection coefficient greater than 15%, a filter with a bandwidth wider than 5% can be realized.

A specific example of a filter device operating at 2.6 GHz with a bandwidth wider than 7% and an in-band ripple of less than 0.6 dB is (100) 300 nm on _{a 1 μm thick SiO 2 layer on a silicon substrate.} Given with a tantalum (Ta) electrode with a thickness of 30 nm on a composite substrate with a thickness of (YXl) / 52 ° LiNbO _{three layers.} In this example, the reflectance coefficient reaches 20% and the binding factor reaches about 18%.

3a-3d are shown in FIG. 2b comprising a composite substrate according to the invention comprising a _{500 nm SiO 2 layer between a 6 μm LiTaO 3} (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate. The characteristics of a surface acoustic wave filter device including a cavity filter structure are shown. This configuration is suitable for operating in the frequency range of 50 MHz to 250 MHz.

In such composite substrates, the true mode of pure shear can be excited and propagated.

For this SAW filter device, the coupled cavity filter structure shown in FIG. 2b is used, i.e., along with the input and output transducer structures, the Bragg mirrors adjacent to each and the four reflections. The structure provides five acoustic cavities that exist between the transducer structures. Both metal strips of each reflective structure and Bragg mirror are connected to each other for short circuit operation.

The staggered transducer structure includes a number of electrode finger pairs set to 15 with an electrode pitch set to 9.95 μm and a ratio a / p set to 0.3. Further, with 30 electrodes, the mirror diffraction grating period is set to 10 μm and a / p is set to 0.4. The gap between the mirror grating and the staggered transducer structure is set to 9 μm, which corresponds to about half a wavelength. The two internal reflective structures, each with 14 electrodes, are separated by a gap g of 4.8 μm corresponding to about a quarter wavelength. Therefore, the aperture is 3.1 mm.

FIG. 3a shows an overall view of the filter transfer function and group delay of the filter as a function of frequency (MHz) from 170 MHz to 250 MHz. Group delay is a measure of phase linearity. FIG. 3b shows an enlarged view of FIG. 3a near the center frequency, thus focusing on bandpass and showing very low transmission loss. Figure 3c shows the signs of the filter poles as a function of a reflection coefficient, as well as the frequency (MHz) (Min _{| S 11} | peak). FIG. 3d is a Smith Abacas diagram of the so-called reflectance coefficient currently used by those of skill in the art for evaluating the electrical impedance matching of both ports of the filter. The reflectance coefficient must be centered around a state of approximately 50 ohms, i.e., the center of the abacus is aligned.

The transfer function in FIG. 3a shows the performance of the device with filter band passage between 210 MHz and 218 MHz. In FIG. 3b, it can be confirmed that the filter band pass shows a flat appearance at about 0.5 dB with low in-band ripple.

FIG. 4 shows a table listing the properties of the coupled cavity surface acoustic wave filter structure shown in FIG. 2b according to the present invention. For all coupled cavity filter structures, the composite substrate used is the same as in FIG. 3, i.e. 6 μm LiTaO ₃ (YXl) / 42 ° piezo layer, semi-infinite with the piezo layer ( 100) It contained _two layers of SiO of 500 nm between the silicon base substrate and the substrate.

The coupled cavity filter structure corresponds to FIG. 2b, i.e., the input and output transducer structures, as well as the adjacent Bragg mirrors and four reflective structures, respectively, between the transducer structures. It brings about five acoustic cavities that exist. Both metal strips of each reflective structure and Bragg mirror are connected to each other for short circuit operation.

All of the coupled cavity filter structures described in FIG. 4 support pure shear wave mode propagation and performance, ie, various filter band passages from 0.5% to 10%, less than 2 dB. Low insertion loss, blocking loss of 15 dB to 20 dB, binding factors greater than 5%, and temperature coefficient (TCF) of frequencies below 20 ppm / K. Bandpasses as large as 10% have a thickness suitable for current deposition techniques, i.e. less than 5% equal to h / λ when h is the pure thickness of the metal strip, eg. It can be achieved using an LNO thin layer containing Pt or W or Ta or Mo based electrodes.

Therefore, to adjust the coupling coefficient for the required performance of the coupled cavity SAW filter device, and to adjust the number and size of reflective structures so as not to exceed the size limit of the coupled cavity filter structure. In addition, it is possible to select the material.

The coupled cavity SAW filter device according to the invention achieves smaller dimensions based on improved miniaturization, while providing a blocking loss of 15 dB to 20 dB and low ripple within the filter bandpass, from 0.5% to. A shear wave of the composite substrate is used to achieve a narrow filter band passband of less than 10% and a low insertion loss of less than 2 dB.

5a and 5b show a coupled cavity surface acoustic wave filter structure according to a third embodiment of the present invention.

In the third embodiment, the coupled cavity surface acoustic wave filter structure 800 is the same as the substrate 102 of FIGS. 1a and 1b, as in the case of the first embodiment shown in FIGS. 1a and 1b. It is realized in the composite substrate 102.

The same reference numerals as those shown in FIGS. 1a and 1b are used to represent the same features and are not repeated in detail.

_{In this embodiment, the thin SiO 2} layer 108 provided at the interface 110 between the piezoelectric layer 104 and the base substrate 106 in order to improve the attachment of the piezoelectric material layer 104 to the base substrate 106 has a thickness of 500 nm. ..

The coupled cavity filter structure 800 includes two transducer structures 812, 814 and two transducer structures 812, at a specific distance L from the transducer structures 812, 814 in the propagation direction X shown in FIG. 5a. It comprises one reflective structure 816 located between 814.

Each transducer structure 812, 814 comprises two electrodes 824, 828 (not shown), each of the two electrodes 824, 828 comprising a plurality of electrode means 828, 830, respectively. The comb tooth electrodes are connected to the + V / −V potential by alternating techniques, with the electrode 824 connected to + V and the electrode 826 connected to −V, or vice versa. In the modified example, the electrodes 824 and 826 may be comb-teeth electrodes, particularly staggered electrodes.

The transducer structures 812, 814 are provided by an electrode pitch p (not shown) corresponding to the inter-edge electrode finger distance between two adjacent electrode fingers 828, 830 from opposed comb tooth electrodes 824 and 828. It is stipulated.

In this embodiment, the electrode pitch p of the transducer structures 812, 814 is defined by a certain number of wavelengths nλ, where λ is the operating acoustic wavelength of the transducer structures 812, 814.

The metal ratio a / p of the transducer structure is defined as the ratio of the electrode width a divided by the electrode pitch p.

In this embodiment of the present invention, reflective structure 816 is realized by the groove 822, the dimension _{L 1} corresponding to the distance between the two side edges walls 822a and 822b of the groove 822, and the total of the groove 822 It is defined by the depth D. The total depth D of the groove 822 is defined between the surface of the piezoelectric layer 104 where the transducers 812 and 814 are located and the bottom surface 822c of the groove 822. The depth D of the groove 822 is on the order of λ or more, particularly on the order of 10λ or more, where λ is the wavelength of the surface acoustic wave.

Further, the groove 822 is further defined by an etching clearance angle θ340 that defines the positions of the groove edge walls 822a and 822b with respect to the horizontal axis X and the bottom surface of the groove 822c. The clearance angle θ840 can be on the order of 70 ° or more, especially on the order of 90 °. FIG. 5a shows a groove 822 with a vertical edge wall corresponding to a 90 ° clearance angle θ340.

Reflective structure 816 and the region 818 with region, a defined width, for example, by a distance _{L 2} that is located between the transducer structure 812, 814 correspond to the acoustic cavity 820. The distance L ₂ is defined as the distance between one edge wall 822a, 822b of the groove 822 and points A, B located on the surface of the piezoelectric layer on which the transducers 812, 814 are located. Points A and B are located at the ends of the pitch of the transducer structures 812 and 814 on the side where the groove 822 is located, as shown in FIG. 5a. Since the electrodes are centered in the pitch, the pitch ends of the transducer structures 812, 814 do not correspond to the ends of the first electrode 830 of the transducer structures 812, 814. For example, if the ratio a / p is 50%, the end of the pitch is located at a distance equal to λ / 8 of the first electrode 830 of the transducer structures 812, 814. FIG. 5b corresponds to FIG. 5a, where the transducer structures 812, 814 include only two electrodes 828 and 830 to more clearly show the region 818 of the acoustic cavity 820.

In the coupled cavity surface acoustic wave filter structure 800, in the coupled cavity filter structure shown in FIGS. 5a and 5b, two acoustic cavities 820 exist in the propagation direction of the acoustic wave.

In this embodiment of the invention, the reflective structure 816 is provided with grooves 822, for example by etching, instead of depositing metal strips as in the first and second embodiments. It will be realized.

The groove 822 is provided in the piezoelectric layer 104 of the composite substrate 102 and in the SiO ₂ layer below the base substrate 106 to a total depth D. D ₁ corresponds to a part of the depth D realized only in the base substrate 106.

In a modification, the groove 822 can be etched down to the surface of the base substrate 106, which is the interface 810 between the _{SiO 2 layer 108 and the base substrate 106, through the piezoelectric layer 104 and only through the SiO 2 layer 108.} Therefore, D ₁ is equal to 0.

In a fourth embodiment, based on the third embodiment, the coupled cavity filter structure 900 further comprises two Bragg mirrors 832, 834. This embodiment is shown in FIG. 6, in which each Bragg mirror 832, 834 has a transducer structure 812 on the side opposite to the side where the reflection structure 816 is located in the sound wave propagation direction X. , 814 is located close to.

Each Bragg mirror 832, 834 is located at a distance s from the transducer structures 812, 814 of the Bragg mirrors 832, 834, respectively. Each Bragg mirror 832, 834 comprises one or more metal strips 836 and is defined by the pitch of the metal strips 836 corresponding to the distance between the metal strips 836 within the Bragg mirrors 832, 834. As with the transducer, the pitch in the Bragg mirrors 832, 834 is defined by centering the metal strip 840 in the pitch.

In this modification, the pitch of the Bragg mirrors 832, 834 is further equal to n times the wavelength λ, and thus nλ.

In this case, on the side where the Bragg mirrors 832 and 834 are located, the wave is reflected with a phase change, whereas on the groove side, the type of reflection depends on the width and depth of the groove.

In a fifth embodiment, based on the third embodiment, the coupled cavity filter structure 1000 comprises two additional grooves 932, 934, each of the additional grooves 932, 934 in the direction of sound wave propagation. In, it is located close to the transducer structures 812 and 814 on the opposite side to the side where the reflection structure 816 is located. This embodiment is shown in FIG.

Each of the additional grooves 932, 834 is located at a distance s from the transducer structures 812, 814 of the additional grooves 932, 834, respectively. Each of the additional grooves 932, 934 is defined by the width L _{3 of} the additional grooves 932, 934 and the total depth D ₃ of the additional grooves 932, 934. The total depth D ₃ of the additional grooves 932, 934 is defined between the surface of the piezoelectric layer 104 where the transducers 812, 814 are located and the bottom surfaces 932c, 934c of the additional grooves 932, 934. .. The depth D ₂ is defined as the depth of the further grooves 932 and 934 from the bottom surface 822c of the groove 822 to the bottom surfaces 932c and 934c of the grooves 932 and 934. Therefore, the total depth D ₃ is _{defined as D plus D 2} , where D is the total depth of the groove 822 of the reflective structure 816. _{The depth D 3} of at least one additional groove (932, 934) is on the order of λ or greater.

In this embodiment of the invention, the reflective structure 816 and the additional grooves 932, 934 are provided with grooves instead of depositing metal strips as in the first and second embodiments. , For example, realized by etching.

Each of the additional grooves 932, 934 is configured to provide total internal reflection of the propagating wave along the propagating direction.

In the modified example, the coupled cavity filter structure is attached to the transducer structures 812 and 814 on one side of the input transducer and on the other side of the side where the reflection structure 816 is located in the propagation direction X of the acoustic wave. It may have a Bragg mirror and a groove, each located in close proximity, and a groove on the side of the output transducer.

The coupled cavity filter device according to one of the third to fifth embodiments operates in the same manner as the coupled cavity filter device according to the first embodiment, but the device is the same as that of the first embodiment. The structural features of the coupled cavity filter device, namely the pitch of the transducer and mirror, and the dimensions of the cavity are configured to satisfy the conditions for exhibiting similar functionality.

This is because in the case of reflection at the edge, the definition of the reflection position is geometrically defined. Therefore, whatever the origin of the phase in the transducer, phase construction occurs only for an integer number of wavelengths. Since the reflection center equivalent to the Bragg mirror shows the phase fluctuation mainly depending on the reflection intensity, it is more difficult to specify the reflection center equivalent to the Bragg mirror. The Bragg mirror's reflection function is defined as the ratio of the reflected wave to the incident wave defined at one edge of the mirror. It is known in the art that the magnitude of the reflectance coefficient at a single electrode of a diffraction grating adjusts the width of the spectral band corresponding to the reflection operation of the grating. However, the phase variation of the reflection function between the start and end of the mirror blocking band is always in the range of π to 2 × π, and the magnitude of the reflection coefficient also affects the phase variation of the reflection coefficient with respect to the frequency. Can be seen to give.

Therefore, reflective structures comprising the metal strips of the first and second embodiments are shown in the third, fourth, fifth, and sixth embodiments. Substituting with a grooved reflective structure results in a state containing multiples of λ for the coupled cavity filter device to function.

All of the modifications of the coupled cavity filter device according to the first embodiment and the second embodiment are coupled according to the third embodiment, the fourth embodiment, the fifth embodiment, and the sixth embodiment. It can also be applied to type cavity filter devices.

8a to 8h show a coupled cavity surface acoustic wave filter structure according to a sixth embodiment of the present invention, and a modification thereof.

The substrates shown in FIGS. 8a and 8b are the same as the substrates 102 of FIGS. 5a, 5b, 6 and 7. The same reference numerals as those in FIG. 7 are used to represent the same features and are not repeated in detail.

In FIG. 8a, the coupled cavity filter structure 1100, like the coupled cavity filter structure 1000, is accompanied by two grooves 932, 934, each located in close proximity to one transducer structure. It comprises two transducer structures 812, 814. The difference from the coupled cavity filter 900 is that a plurality of reflective structures, ie, two reflective structures 1006 and 1016, are present between the transducer structures 812 and 814. Each reflective structure 1006,1016 plurality of reflective structure corresponds to the groove 1022 are defined by the width _{L 1} and the total depth D of the groove 1022.

These reflective structures 1006 and 1016 are separated from each other by a gap g in the propagation direction X. The region 1008 located between the two adjacent reflective structures 1006, 1016 having the width defined by the gap g corresponds to the acoustic cavity 1010. The acoustic cavity 1010 can be thought of as the central cavity, whereas the cavity 1020 can be referred to as the side cavity.

As with the coupled cavity filter structures 800 and 900, the region 1018 located between the reflective structures 1006 and 1016 and the adjacent transducer structures 812 and 814 is the edge of the reflective structures 1006 and 1016. and further corresponding to the acoustic cavity 1020 having a point located on the surface of the piezoelectric layer 104 a, a defined width by the distance L ₂ between the B.

The region 1008 actually includes the piezoelectric layer 104 and the SiO ₂ layer 108 on the base substrate 106.

Therefore, in the coupled cavity surface acoustic wave filter structure 1100, the three cavities are separated by the reflective structure and exist in the direction of acoustic wave propagation, or otherwise, the cavities are two between the transducers. Surrounded by reflective structures.

In another modification of the sixth embodiment, the coupled cavity surface acoustic wave filter structure 1200 does not include the piezoelectric layer 104 and does not include the SiO ₂ layer 108, as shown in FIG. 8b, the groove 1006. Includes a region 1008 between and groove 1016. Only the base substrate 106 is present in the region 1008. According to a further modification, the surface of the base substrate may be etched so that the thickness of the base substrate in the region 1008 is smaller than the thickness in the region 1018.

For all of FIGS. 8c-8h showing further modifications including subcavities, coupled cavity filter structures 1300-1800 are shown in 2D plan view from above.

In the coupled cavity filter structure 1300 shown in FIG. 6c, two reflection structures 1206 and 1216 among the plurality of reflection structures are separated from each other by a gap w in the propagation direction Z. Region 1208 may or may not be etched, similar to Region 1008 in FIG. 8a. In this case, the acoustic cavity 1020 is divided into two subcavities 1020a and 1020b.

In the coupled cavity filter structure 1400, a plurality of reflection structures 1316 are separated from each other by a gap g in the propagation direction X as in the case of the cavity filter device 1100, and a plurality of reflection structures 1316 are separated from each other by a gap g as in the case of the cavity filter device 1200. The reflective structures 1316 are further separated from each other by a gap w, albeit in the propagation direction Z. The region 1308 between the plurality of reflective structures may or may not be etched, similar to the region 10008 in FIG. 8a and the region 1210 in FIG. 8c.

In this modification, the acoustic cavities 1310 and 1320 are divided into a plurality of subcavities 1310a, 1310b, 1320a and 1320b, similarly to the device 600 according to the second embodiment of the present invention.

In the coupled cavity filter structure 1500, as shown in FIG. 8e, the plurality of reflective structures 1506, 1516 spans the total distance between the two transducer structures 812, 814 in which the reflective structures 1506, 1516 are absent. It is separated symmetrically by a central region 1510 having a width _{w 1} in a direction Z. Further, instead of being a long etched groove in the Z direction as in the modified example described above, the groove 1522 in this example is square. For clarity, only one reflective structure 1506, 1516 and one groove 1522 are shown in FIG. 8e.

In the coupled cavity filter structure 1600 shown in FIG. 8f, the dimensions of the region 1610 not including the reflection structures 1506 and 1516 between the transducer structures 812 and 814 are different from the region 1510 in FIG. 8e. Region 1610 is actually thinner and the three reflective structures are removed in rows in the Z direction. Region 1610 can be the same as the break in the symmetry of the plurality of reflective structures. For clarity, only one reflective structure 1506, 1516 and one groove 1522 are shown in FIG. 8f.

In another variant, the device 1700 shown in FIG. 8g corresponds to the device 1500 of FIG. 8e, with a plurality of reflective structures 1506, 1516, and thus two additional grooves with a plurality of grooves 1522. Includes 1532 and 1534.

In a variant of the invention, the coupled cavity filter structure 1800 may include three or even more transducer structures. FIG. 8h shows a modification in which the three transducer structures 1210, 1212, 1214 are present in the coupled cavity filter structure 1200.

Two of the transducer structures 1210, 1214 are located outside the reflective structures 1706, 1716, as in the structure of FIG. 2c, and the third transducer structure 1212 is a reflective structure. Located in the center of objects 1706, 1716, therefore, there is one reflective structure 1706, 1716 on each side of the third transducer structure 1212, and thus a groove 1722. The transducer structure 1212 further comprises the transducer structures 1210, 1214 and the adjacent reflection structures of the transducer structures 1210, 1214, respectively (in this example, the 1706 and the transducer structure relative to the transducer structure 1210). The distance L corresponding to the same distance from 1716) to 1214) is separated from the two adjacent reflective structures 1706, 1716. Such a cavity filter structure 1800 is symmetric and results in stronger confinement of energy in the cavity 1720 as compared to the cavity filter structure 1300 shown in FIG. 8c, which contains only two transducer structures 812, 814. Further, in this example, reflective structure 1706,1716 is further similarly distance _{w 1} spaced from each other as in the device 1300 shown in FIG. 8c.

In a modification of the present invention, the coupled cavity filter structure is not symmetrical because the third transducer 1210 is not located in the center of the coupled cavity filter structure.

FIG. 9 shows a device according to a third embodiment of the present invention used for simulation.

For this simulation, the device used corresponds to the device 1000 shown in FIG. 7, but in this example the transducer structures 812 and 814 have only two electrode fingers 828, 830, respectively. ..

In addition, the following parameters were used for the structure. _{A composite substrate containing a 200 nm SiO 2} layer between a 500 nm LiTaO ₃ (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate was used for the simulation. The electrode pitch p of the transducer is equal to 800 nm, achieving a wavelength λ equal to 1.6 μm for frequency operation near 2.5 GHz. The metallized body ratio a / p is equal to 0.5, which means that the electrode width of a is equal to 400 nm. The electrode finger is Al-Cu having a thickness set to 100 nm.

10a and 10b show the simulated characteristics of the coupled cavity surface acoustic wave filter structure shown in FIG. 9 according to an example of the third embodiment of the present invention.

In this practical example, pitch p equal to 2 μm, depth D _{1 equal to pitch p, depth D 2} equal to 6 × p, _{width of groove L 1} equal to 6.4 μm, and equal to 2 × p. Simulations were performed using a mesh structure with a width L _{2 (not shown).} (100) A composite substrate containing _{LiTaO 3 having} a thickness of 600 nm _{and SiO 2} having a thickness of 500 nm was used on a Si base substrate.

FIG. 10a shows a graph of admittance with a real part on the left Y-axis and an imaginary part on the right axis as a function of frequency expressed in GHz on the X-axis. FIG. 10a shows two peaks at about 61800 GHz and 62000 GHz, with the peak at about 61750 GHz showing stronger admittance than the other peak at about 62000 GHz.

FIG. 10b shows a graph of mutual admittance with a real part on the left Y-axis and an imaginary part on the right axis as a function of frequency expressed in GHz on the X-axis. FIG. 10b shows the same two peaks at about 61800 GHz and 62000 GHz, but in this case with a more balanced contribution, the two peaks are comparable in amplitude.

The graph shows two combined modes, and the two well-balanced contributions allow for effective regulation of filter band passage, regardless of the actual amplitude level.

11a-11d show the calculation of the admittance of the filter basic structure for various dimensions of the reflective structure according to the present invention.

A composite substrate containing a _{500 nm SiO 2} layer between a 600 nm LiTaO ₃ (YXl) / 42 ° piezoelectric layer and a semi-infinite (100) silicon substrate was used for simulation.

Figure 11a~ Figure 11b, to the depth D ₁ of the various grooves, as a function of frequency expressed in GHz in the X-axis, taking the real part to the left of the Y-axis, taking the imaginary part to the right of the shaft The graph of admittance is shown. The frequency range shown is between 61000 GHz and 63000 GHz. All graphs show the same two peaks at about 61800 GHz and 62500 GHz as in FIG. 10b, and the graphs show a double peak morphology in which the first peak at about 61800 GHz has a higher admittance value than the second peak at about 63000 GHz. It can be considered. In FIG. 10d, the double peak actually has a thinner bandwidth than in FIG. 11a, FIG. 11b, or FIG. 10c.

In FIGS. 11a-11c, D ₁ fluctuates between 1 μm and 0.2 μm, whereas in FIG. 11d, D ₁ fluctuates between 1 μm and 2 μm.

In FIGS. 11a to 11d, the same behavior of the peak can be confirmed. As D ₁ decreases from 1 μm to 0.2 μm, the double peak morphology moves towards higher frequencies, the first peak becomes smaller in terms of admittance, and the second peak becomes larger in terms of admittance. In FIGS. 11b, 11c, and 11d, the second peak is larger in terms of admittance so that the second peak actually reaches a value higher than the first peak, whereas in FIG. 11a, Both peaks are equivalent for _{D 1} equal to 0.2 μm.

12a and 12b show an example of the SAW ladder filter device according to the prior art in FIG. 12a and an example of the SAW ladder filter device according to the present invention in FIG. 12b.

In FIG. 12a, each of the four transducer structures 1612, 1614, 1616 and 1618 is sandwiched between the two reflective structures 1632 and 1634. The staggered electrodes of the transducers 1612, 1614, 1616, 1618 are connected to each other by metal wires 1640. As can be seen, the transducer and the metal connection of the transducer require a lot of space, so such a design is bulky. Transducers cannot be aligned on a single vertical or horizontal line as they need to be shifted from one to another to allow connections between the transducers. ..

FIG. 12b shows a SAW ladder filter device 2000 in which two cavity-coupled filter devices 1000 according to the present invention are located close to each other on a single line. Each cavity-coupled filter device 1000 comprises two transducer structures 1712, 1714 and 1716, 1718, respectively, and their respective reflection structures 1732, 1734 and 1716. The reflective structure 1716 is located between the two transducer structures, eg, 1716 is located between 1712 and 1714, and the reflective structures 1732 and 1734 are on the side where the reflective structure 1716 is located, respectively. On the other side, it is located on one side of the transducer structure. In FIG. 12b, the reflective structures 1716, 1734, and 1732 are represented as grooves as in the case of FIG. As in the case of FIG. 12a, the electrodes of the transducer are connected to each other by a metal wire 1740.

Although the SAW ladder filter device 2000 including two cavity coupled filter devices 1000 is shown in FIG. 12b, any modification of the cavity coupled filter device 1000 according to the present invention is used for the SAW ladder filter device. obtain.

The SAW ladder filter device 2000 according to the present invention is smaller and does not require as much space as the SAW ladder filter device shown in FIG. 12a.

Many embodiments of the invention have been described. Nevertheless, it is understood that various modifications and improvements may be made without departing from the claims described below.

Claims (37)

With the acoustic wave propagation substrate (102),
At least one input transducer structure (112, 506) and one output transducer structure (114, 506) provided on the acoustic wave propagation substrate (102), which are staggered comb tooth electrodes. At least one input transducer structure (112, 506) and one output transducer structure (114, 506), each comprising (124, 126, 508, 510).
One reflection structure (116), wherein the reflection structure (116) is the input transducer structure (112, 506) and the output transducer structure (114, 506) in the propagation direction of the acoustic wave. ) At a distance d and at least one groove (122) located between the input transducer structure (112, 506) and the output transducer structure (114, 506). Two reflective structures (116) and
In a coupled cavity filter structure using surface acoustic waves, particularly waveguideed surface acoustic waves.
A coupled cavity filter structure, wherein the acoustic wave propagation substrate (102) is a composite substrate including a base substrate (106) and a piezoelectric layer (104). The surface acoustic wave is configured to be a shear wave or longitudinal wave in the piezoelectric layer (104), particularly a waveguide shear wave or a waveguide longitudinal wave in the piezoelectric layer (104). , The coupled cavity filter structure according to claim 1. The staggered comb tooth electrodes (124, 126) of the at least one input transducer structure (112) and the one output transducer structure (114) are given by p = λ / 2 in the Bragg condition. Λ is the operating acoustic wavelength of the input transducer structure (112) and the output transducer structure (114), and p is the input transducer structure (112) and the output transducer. The coupled cavity filter structure according to claim 1 or 2, which is an electrode pitch of the structure (114). The input transducer structure (112) and / or the output transducer structure (114) is on the opposite side of the side where the one reflection structure (116) is located in the propagation direction of the acoustic wave. The coupled cavity filter structure according to any one of claims 1 to 3, further comprising at least one Bragg mirror (132, 134) located away from. Distance d from the input transducer structure (112, 506) and the output transducer structure (114, 506) in the propagation direction of the acoustic wave and separated from each other by a gap g, and the input transformer. The reflection structure (116, 202, 204, 206, 208, Each of the gap g between 302, 304, 306, 308, 310, 312, 402, 404, 408), the input transducer structure (112), the output transducer structure (114), and the input transformer. Each gap d between the Ducer structure (112) and the adjacent reflection structure of the output transducer structure (114) forms an acoustic cavity (120, 212, 214, 316, 408). , The coupled cavity filter structure according to any one of claims 1 to 4. In particular, the phase velocity in the acoustic cavity (120, 212, 214, 316, 408) is such that the reflective structure (116, 202, 204, 206, 208, 302, 304, 306, 308, 310, 312, 402, In any one of claims 1 to 5, the dimensions of each of the acoustic cavities (120, 212, 214, 316, 408) are smaller than λ / 4 so as to be greater than the phase velocity within 404, 408). The coupled cavity filter structure described. The distance g and / or the distance g between adjacent reflection structures (202, 204, 206, 208, 302, 304, 306, 308, 310, 312, 402, 404, 408) of the plurality of reflection structures. , The input transducer structure (112, 506) in close proximity to the reflection structure (116, 202, 204, 206, 208, 302, 304, 306, 308, 310, 312, 402, 404, 408) and said. The coupled cavity filter structure according to claim 5 or 6, wherein the distance d from the output transducer structure (114, 506) is the same or different. The reflective structure (116) or the reflective structure (202, 204, 206, 208, 302, 304, 306, 308, 310, 312, 402, 404, 408) is the composite substrate (102) and the input. transducer structure (112,506) and the larger coupling coefficient _k ^{s 2} associated with comb electrodes (124,126,604,606) of said output transducer structures (114,506), the unitary metal strip associated reflection coefficient, in particular, the with coupling coefficient k _s at least 1.5 times greater reflection factor than ^2, coupled cavity filter structure according to any one of claims 1 to 7. Each of the reflective structures (116, 202, 204, 206, 208, 302, 304, 306, 308, 310, 312, 402, 404, 408) of the plurality of reflective structures comprises at least one or more metal strips. (122, 210), wherein the pitch of the metal strip is the same as or different from the electrode pitch p of the input transducer structure and the output transducer structure (112, 114, 506). The coupled cavity filter structure according to any one of 1 to 8. The metal strip (124) of each of the reflective structures (116, 202, 204, 206, 208, 302, 304, 306, 308, 310, 312, 402, 404, 408) of the plurality of reflective structures. 9. The coupled cavity filter structure according to claim 9, wherein they are electrically connected to each other. Each of the reflective structures (116, 202, 204, 206, 208) of the plurality of reflective structures so that the reflectance of the plurality of reflective structures is greater than 0.5, particularly greater than 0.8. , 302, 304, 306, 308, 310, 312, 402, 404, 408), wherein the number of metal strips (122, 210) is less than 30, preferably less than 20, any of claims 1-10. The coupled cavity filter structure according to item 1. The difference between the acoustic impedance of the material from the piezoelectric layer (104) and the acoustic impedance of the material from the metal strips (122, 210) of the plurality of reflective structures is the reflectance coefficient of the plurality of reflective structures. The coupled cavity filter structure according to any one of claims 1 to 11, wherein is configured to be greater than 0.5, particularly greater than 0.8. With the acoustic wave propagation substrate (102),
At least one input transducer structure (812) and one output transducer structure (814) provided on the acoustic wave propagation substrate (102), each comprising electrodes (824, 828). With at least one input transducer structure (812) and one output transducer structure (814),
One reflection structure (816), wherein the reflection structure extends from the input transducer structure and the output transducer structure (812, 814) to a distance L in the propagation direction of the acoustic wave. A reflection structure (816) comprising a groove (822) located between the input transducer structure and the output transducer structure (812, 814).
In a coupled cavity filter structure using surface acoustic waves, particularly waveguideed surface acoustic waves.
A coupled cavity filter structure, wherein the acoustic wave propagation substrate (102) is a composite substrate (102) including a base substrate (106) and a piezoelectric layer (104). The surface acoustic wave is configured to be a shear wave or longitudinal wave in the piezoelectric layer (104), particularly a waveguide shear wave or a waveguide longitudinal wave in the piezoelectric layer (104). The coupled cavity filter structure according to claim 13. The electrodes (824,826) of at least one input transducer structure (812) and one output transducer structure (814) are defined by an electrode pitch p equal to nλ, where λ is said. The coupled cavity filter structure according to claim 13 or 14, which is the operating acoustic wavelength of the input transducer structure (812) and the output transducer structure (814). The input transducer structure (812) and / or the output transducer structure (814) is on the opposite side of the side where the one reflection structure (816) is located in the propagation direction of the acoustic wave. The coupled cavity filter structure according to any one of claims 13 to 15, further comprising at least one additional groove (932, 934) located away from. The input transducer structure (812) and / or the output transducer structure (814) is on the opposite side of the side where the one reflection structure (816) is located in the propagation direction of the acoustic wave. 16. The coupled cavity filter structure of claim 16, _{wherein the depth D 3 of} at least one additional groove (932, 934) located away from is on the order of λ or greater. In the propagation direction of the acoustic wave, the gap g is separated from each other, and the distance L from the input transducer structure (812) and the output transducer structure (814), and the input transducer structure. A plurality of reflective structures (1006, 1016, 1206, 1216, 1306, 1316, 1416, 1616) located between (812) and the output transducer structure (814) are provided, and the reflective structure (1006) is provided. 10.16, 1206, 1216, 1306, 1316, 1416, 1616), each said gap g forms an acoustic cavity (1010, 1210, 1310, 1410, 1510, 1710), claims 13-17. The coupled cavity filter structure according to any one of the above. The input transducer structure (812) and the output transformer on the edge of the groove (822, 1022, 1322, 1422, 1522, 1722) and on the side where the groove is located in the propagation direction of the acoustic wave. position a corresponding to the ends of the pitch of Deyusa structure (814), the distance _{L 2} between the B, and an acoustic cavity (820,1020,1220,1320,1420,1520,1620,1720) The coupled cavity filter structure according to any one of claims 13 to 18. 16. The distance between the edge of the groove (822, 1022, 1322, 1422, 1522, 1722) and the edge of at least one further groove (932, 934) is on the order of nλ, claim 16. The coupled cavity filter structure according to any one of 19 to 19. The clearance angle θ (840) of the groove (822, 1022, 1322, 1422, 1522, 1722) of the reflective structure (816, 1006, 1016, 1206, 1216, 1306, 1316, 1416, 1616). 13. The coupled cavity filter structure according to any one of 20 to 20. The depth D of the groove (822, 1022, 1322, 1422, 1522, 1722) of the reflective structure (816, 1006, 1016, 1206, 1216, 1306, 1316, 1406, 1416, 1506, 1516, 1716) , Λ or more, particularly the coupled cavity filter structure according to any one of claims 13 to 21, wherein λ is the wavelength of the surface acoustic wave. The coupled cavity according to any one of claims 16 to 22, wherein the at least one additional groove (932, 934) is configured to provide total reflection of the propagated wave along the propagating direction. Filter structure. The acoustic cavity (1010) formed between at least two grooves (1022, 1322, 1422, 1522, 1722) of the plurality of reflective structures (1006, 1016, 1206, 1216, 1306, 1316, 1416, 1616). , 1210, 1310a, 1310b, 1410, 1510, 1710) is the acoustic wave propagation substrate (812, 814, 1210, 1212, 1214) on which the input transducer structure and the output transducer structure (812, 814, 1210, 1212, 1214) are located. The coupled cavity filter structure according to any one of claims 18 to 23, which is located on the surface of the acoustic wave propagation substrate (102) which is also the surface of 102). The acoustic cavity (1010) formed between at least two grooves (1022, 1322, 1422, 1522, 1722) of the plurality of reflective structures (1006, 1016, 1206, 1216, 1306, 1316, 1416, 1616). , 1210, 1310a, 1310b, 1410, 1510, 1710) are the surface of the acoustic wave propagation substrate (102) and the bottom surface of at least two said grooves (1022, 1322, 1422, 1522, 1722) located at a depth D. The coupled cavity filter structure according to any one of claims 18 to 24, which is located at a depth included between (1022c) and. The input transducer structure and the output transducer structure (112, 114, 506, 812, 814, 1210, 1214) are different from each other, and in particular, the input transducer structure and the output transducer structure (112,). The coupled cavity filter structure according to any one of claims 1 to 25, wherein each of 114, 506, 812, 814, 1210, 1214) has a different number of electrode fingers (128, 130, 828, 830). .. The coupled cavity filter structure according to any one of claims 1 to 26, wherein the acoustic cavity can be divided into subcavities (1310a, 1310b) separated from each other. A claim comprising the input transducer structure and the output transducer structure (112, 114, 314, 506, 814, 812, 1210, 1212, 1214) in the propagation direction of the acoustic wave. The coupled cavity filter structure according to any one of 1 to 27. The shear wave in the piezoelectric layer (104), in particular, of the guided shear waves, or as an electromechanical coupling coefficient k _s ² of waveguided longitudinal wave is greater than 5%, greater than in particular 7% As such, the characteristics of the piezoelectric layer (104), and the electrodes (112, 114, 314, 506, 814, 812, 1210, 1212, 1214) of the input transducer structure and the output transducer structure (112, 114, 314, 506, 814, 812, 1210, 1212, 1214). The coupled cavity filter structure according to any one of claims 1 to 28, wherein the characteristics of 124, 126, 508, 510, 824, 826) are selected. Shear waves in the piezoelectric layer (104), in particular, of the guided shear waves, or electromechanical coupling factor k _s ² of waveguided longitudinal wave, to be greater than 5%, greater than in particular 7% The coupled cavity filter structure according to any one of claims 1 to 29, wherein the thickness of the piezoelectric layer (104) is selected so as to be. The coupling type according to any one of claims 1 to 30, further comprising a dielectric layer (108) sandwiched between the base substrate (106) and the piezoelectric layer (104), particularly a SiO _{2 layer.} Cavity filter structure. The piezoelectric layer (104) is aluminum nitride (AlN), zinc oxide (ZnO), PZT, gallium tantalate (GaN), lithium tantalate LiTaO ₃ , or lithium niobate LiNbO ₃ , and lithium tantalate LiTaO ₃ or niobate. lithium LiNbO ₃ has a crystal orientation with respect to (YXl) / θ lithium tantalate LiTaO ₃ or lithium niobate LiNbO _3, which is defined as according to the standard IEEE1949Std-176, the angle of the crystal orientation theta is, 0 ° to 60 ° The coupled cavity filter structure according to any one of claims 1 to 31, which is between, or between 90 ° and 150 °. 1. The base substrate (106) of the composite substrate (102) is one of silicon, particularly a high resistivity silicon substrate including a trap-rich layer, carbon diamond, sapphire, quartz, or silicon carbide. The coupled cavity filter structure according to any one of No. 32. The coupled cavity filter structure according to any one of claims 1 to 33, wherein the base substrate (106) is provided with a Bragg mirror below the piezoelectric layer (104). The coupled cavity filter structure according to any one of claims 1 to 34, wherein the filter band passage is included between 0.5% and 10%. Further, a passion layer formed on the input transducer structure and the output transducer structure (112, 114, 314, 506, 814, 812, 1210, 1212, 1214) and at least the one reflective structure. The passage layer is on the input transducer structure and the output transducer structure (112, 114, 314, 506, 814, 812, 1210, 1212, 1214) and / or at least the one reflective structure. The coupled cavity filter structure according to any one of claims 1 to 25, which has the same or different predetermined thickness. A SAW ladder filter device comprising at least two coupled cavity filter structures according to any one of claims 1 to 35, wherein the at least two coupled cavity filter structures are located on a single line. SAW ladder filter device.

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